1. Field of the Invention
The present invention relates to an articulator for use in a process for manufacturing a dental product (hereinafter called "upper and lower jaw models"), such as a preserved dental article, a dental prosthesis or an orthodontics device, for the upper and lower jaw teeth for a dental patient.
2. Related Background Art
Dentures or the like are manufactured by performing a stereoscopic adjustment using an articulator to be adaptable to the characteristic of the shapes of the jaws of each patient so that malocclusion is prevented. In general, the articulator incorporates a lower jaw frame provided with a lower-jaw-model mount to which a lower jaw model is joined; and an upper jaw frame which constitutes a Frankfort plane, which is rotatively combined with the lower jaw frame and which is provided with an upper-jaw-model mount to which an upper jaw model is joined. The articulator incorporates an incisal pin which is provided for the upper jaw frame and arranged to be brought into contact with an incisal table provided for the lower jaw frame so that the vertical positions of occlusion planes of the lower jaw model and the upper jaw model are determined.
The articulator is arranged to accurately reproduce complicated anatomical motions of jaws so as to manufacture a further accurate upper and lower jaw models, such as a dentures. Therefore, the articulator is structured such that a variety of complicated adjustment mechanisms are provided for the above-mentioned basic elements.
For example, in Japanese Patent Laid-Open No. 7-95990, an articulator has been disclosed, in which a lower-jaw-model support frame, to which a lower jaw model is joined, and an upper-jaw-model support frame, to which an upper jaw model is joined, can be adjusted in terms of the relative rotational directions, combination of angles in a vertical direction and the fore-and-aft positions. Therefore, the upper- and lower-jaw-model support frames are supported by upper and lower frames through slide mechanisms and spherical joints. Moreover, in Japanese Utility-Model Publication No. 6-36812 having a title "ARTICULATOR", an articulator has been disclosed which has a structure that upper and lower frames are slidably supported by a stand in fore-and-aft directions. Moreover, an upper-jaw-model support frame, to which the upper jaw model is joined, and a lower-jaw-model support frame, to which the lower jaw model is joined, are rotatively supported by upper and lower frames.
As described above, in order to accurately reproduce complicated motions of the jaws, the conventional articulator must have a variety of adjustment mechanisms. Therefore, the conventional articulator has problems in that the number of required elements cannot be decreased, the overall structure becomes too complicated, the overall cost cannot be reduced and the operability and durability deteriorate. Since the conventional articulator is a costly apparatus, a multiplicity of the articulators cannot easily be provided for a dental clinic or the like. Therefore, whenever upper and lower jaw models are manufactured for each patient, the upper and lower jaw models must be changed. Thus, the efficiency deteriorates excessively.
In general, the articulator is used to manufacture dentures or the like by using upper and lower jaw models and plaster. When, for example, the dentures are manufactured, water is used in a large quantity in a cleaning process. Therefore, the articulator must be manufactured in such a manner that powder and broken pieces of plaster and the like can easily be removed. Moreover, rust prevention is required. Since the conventional articulator is provided with a variety of complicated adjustment mechanisms, there arises a problem in that powder and broken pieces of plaster introduced into the adjustment mechanism cannot easily be removed, a breakdown takes place and rust is formed.
For example, the articulator disclosed in Japanese Patent Laid-Open No. 7-95990 has the structure that each of the support frames to which the upper and lower jaw models are joined is supported by the frame through the spherical joint. Thus, there is apprehension that powder and broken pieces of plaster will be introduced into the spherical joint and thus each support frame cannot smoothly be operated for performing the adjustment process. What is worse, the relative positioning accuracy deteriorates in the foregoing case. The articulator disclosed in Japanese Utility-Model Publication No. 6-36812 has a problem in that the upper and lower frames cannot smoothly be slid with respect to the stand. Since the upper jaw model serving as a reference is moved when the upper and lower jaw models are manufactured, the reference position cannot be defined. Thus, there arises a problem in that the adjustment operation cannot easily be performed.
It is preferable that the articulator has satisfactory operability and ease of maintenance as compared with a structure having a multiplicity of functions. Moreover, excellent durability and cost reduction have been required. That is, the articulator is not required to have functions which are capable of completely reproducing the complicated motions of the jaws. The upper and lower jaw models are simply required to be manufactured such that the occlusion of a patient can satisfactorily be reproduced. Moreover, the articulator only needs to perform those functions which enable correction and adjustment of the occlusion.
The articulate ligamentum positioned between the maxilla and the mandible is shifted together with the mandible when the lower jaw is moved. Therefore, correction or adjustment of the upper and lower jaw models is performed in consideration of the above-mentioned shift by using the articulator. The inventor of the present invention has studied the shift of the articulate ligamentum. As a result, attention is paid to a fact that the main movement of the lower jaw of a major portion of patients is a substantially rotational motion in the horizontal direction with respect to a Frankfort plane such that substantially the center of the lower jaw is the center of the rotational motion.
Therefore, the articulator must have a function which is able to rotate the lower jaw model in the horizontal direction around the center of the lower-jaw-model support frame, to which the lower jaw model is joined, the lower jaw model being rotated with respect to the Frankfort plane of the upper frame. As a matter of course, the articulator is provided with a function for rotating the upper frame with respect to the lower frame and a function for adjusting the height of occlusion or occlusion in the fore-and-aft direction to easily manufacture the articulator.
Since the articulator is frequently manipulated when the upper and lower jaw models are manufactured or when correction or adjustment is performed, the articulator must easily be held and handled. Since the conventional articulator has the function for accurately reproducing the motion of the jaws as an important function, the conventional articulator is provided with complicated mechanisms. Therefore, the conventional articulator cannot easily be held and handled and the weight reduction cannot easily be realized. As a result, there arises a problem in that the operability of the conventional articulator is unsatisfactory.